Yes! there are women composers! So, why do the text/piano books not mention them? Well, they do mention them, but very briefly.
Clara Schumann lived during the 19th century and was called “the high priestess of music” giving her first complete piano recital at the age of 11 and enjoying 61 years of concert life.
“Throughout her life, Clara was well-known as a piano soloist, gaining fame for her technical proficiencies, sensitive interpretations of musical works and her ability to express the composer’s intent in the music. During her lifetime, she premiered pieces by Frederic Chopin, Johannes Brahms and her husband, Robert Schumann. A composer herself, Clara wrote 66 pieces, including works for piano and orchestra, solo piano and even cadenzas for piano concertos already written by Beethoven and Mozart! Widely respected for her musical opinions, both Clara’s husband and Brahms sought her advice and guidance when writing music.” DSO
Enjoy a performance of her Romanza 1, Op. 11 found on YouTube.